The present invention pertains to the suppression of undesirable fugitive emissions that is prevalent in the production of molten metal, particularly that of iron or steel.
When molten metals are subjected to turbulent flow as, for example, molten iron in flowing along a runner system between a blast furnace and a tapping ladle a significant amount of undesirable fume is generated that constitutes a serious atmospheric pollution problem, the abatement of which represents a substantial part of the cost of performing the process. Much effort and expense has been expended in the development of emission control systems effective to maintain the volume of this fugitive fume within acceptable limits. Past efforts have been primarily directed toward the development of systems that collect the fume after it has been generated and conduct it to treating apparatus for cleaning it prior to its discharge into the atmosphere. Such systems, while been effective to a limited degree in solving the concerned problem, are expensive to install and costly to operate.
More recently, however, developments have been made in apparatus that is effective to dispense with the need for fume collection and treatment apparatus by preventing the formation of fume in the first instance. Such apparatus is described in Japanese Pat. No. 53-6602, granted Mar. 9, 1978 to Nippon Steel Corporation in which fume is suppressed by blanketing the molten bath with inert gases, such as steam or nitrogen. U.S. patent application Ser. No. 286,395, filed July 23, 1981 by Ball et al teaches fume suppression by injecting a mixture of water and inert gas over the molten bath in a receiver. U.S. patent application Ser. No. 325,460 filed Nov. 27, 1981 by Billings et al describes a comparable system in which fuel is burned over the molten bath in order to consume the ambient air and thereby deprive the bath of air available for fume formation.
Belgian Pat. No. 889,880 issued Dec. 1, 1981 to Vajda describes a fume suppression system suitable for use on the pouring trough and runner system of a blast furnace cast house. According to the teachings of this patent, the pouring trough and the iron and slag runners are covered by various devices including mechanical covers, blankets of inert gas, and other elements in order to isolate the molten streams flowing therein from ambient air. The use of such devices, however, are not completely desirable for various reasons. Mechanical covers suitable for this use are large, heavy members that require frequent removal and replacement. This need to frequently move the covers is costly in the time and effort involved. The need to frequently repair and/or replace the covers represents a significant operating expense. Moreover, such movement of the covers disturbs the seal required between the cover edges and the runners thereby creating a danger of air leakage at the respective interfaces between the covers and the runners which renders the system ineffective. Additionally, the provision of inert gas ejector manifolds over the length of the runners, besides being subject to damage caused by excessive heating, are also prone to failure due to molten metal splattering that, over time, causes the ejector opening to plug.
It is to the amelioration of the above problems and toward the provision of a more suitable molten metal fume suppression apparatus for use over blast furnace cast house runners that the present invention is directed.